Efficient Pd<sup>0</sup>-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases
作者:Philipp M. Holstein、Maria Vogler、Paolo Larini、Guillaume Pilet、Eric Clot、Olivier Baudoin
DOI:10.1021/acscatal.5b00898
日期:2015.7.2
New binepine ligands have been synthesized, and characterized and have been shown to induce high diastereo- and enantioselectivity in the intramolecular arylation of primary and secondary C(sp3)–H bonds, giving rise to fused cyclopentanes. The ligands were obtained as bench-stable phosphonium tetrafluoroborate salts that can be directly employed in catalysis. It was shown that a ferrocenyl P-substituent
合成,表征和表明新的inepinepine配体在初级和次级C(sp 3的分子内芳基化反应中诱导高非对映选择性和对映选择性)– H键,产生稠合的环戊烷。获得的配体为可稳定用于四氟硼酸的四氟硼酸bench盐。结果表明,在前所未有的低温(90°C)和催化剂负载(1-2 mol%Pd)下,配体上的二茂铁基P-取代基与碳酸钾结合可实现较高的立体选择性,使碳酸氢键芳基化/ 2–3 mol%的配体)。使用无碱的预催化剂,表明碳酸盐是活性碱,并且比乙酸盐和新戊酸酯提供更高的立体选择性。还可以实现更困难的仲C–H键芳基化,并需要对配体结构和碳酸盐抗衡阳离子进行微调。该方法允许产生包含三个相邻的立体中心作为单个非对映异构体并且具有中等至高对映选择性的稠合三环产物。实验数据表明,对映体确定C–H活化步骤涉及单连接物种。使用典型的Binepine配体进行DFT(PBE0-D3)计算,以了解对映选择性的起源。对主要